1. Field of the Invention
This invention relates to a high-voltage transformer, especially for a diagnostic radiology generator and high-voltage supply units. The high-voltage generator of the type considered is supplied by a converter which is capable of operating at relatively high frequencies having maximum values in the vicinity of 100 kilohertz, for example.
2. Description of the Prior Art
A high-voltage transformer must not only have the requisite characteristics for the operation to be performed but must also entail low capital outlay in regard to raw materials and production costs, particularly in the case of industrial manufacture. These conditions are more difficult to satisfy as the high-voltage transformer has to meet more stringent design requirements of compactness and small size. The dimensions of a high-voltage transformer can be reduced in particular by optimizing the dimensions of the magnetic circuit or core employed, by choosing suitable material for the fabrication of this latter as well as a suitable operating frequency which can be made much higher than that of the power supply system by making use of a converter.
In fact, one of the determining parameters in the construction of a transformer is the magnetic sheet loss. Thus, the lower the losses and the higher the value of induction which can be chosen without exceeding the permissible tolerance of iron losses.
The high-frequency converter technique permits the use of relatively small magnetic circuits or cores, thus facilitating compact construction of the high-voltage transformer. In accordance with customary practice, the high-frequency converter delivers into a load circuit which includes the primary winding of the high-voltage transformer and an oscillating circuit, the resonance frequency of said oscillating circuit being related to the operating frequency of the converter. The frequency limits within which the converter is capable of operating are determined in particular by the semiconductors employed. Operating frequencies up to 100 kilohertz can be controlled without any problem by thyristors of the type in use at the present time.
However, as the dimensions of the high-voltage transformer are smaller in respect of a given value of high voltage, so it becomes more difficult to establish electrical insulation between the secondary winding and the primary winding and the transformer core so that, in the case of small dimensions of the transformer, this latter attains very high cost levels both in regard to the price of materials employed and in regard to complexity of operations involved in assembly.